In an ink jet recording method, droplets of ink are generated and scattered by various ink (recording liquid) jet steps, for example, an antistatic suction step, a step of applying mechanical vibration or displacement to ink upon using a piezoelectric element and a step of utilizing a pressure generated by bubbling ink through heating, and a part or all of the droplets are adhered to a recording medium such as paper for recording. This method has been rapidly applied to a variety of facsimiles or printers in recent years because noise is reduced, high-speed recording is possible, a full color is easily obtained, a hard copy can easily be provided, and coloration can be conducted at a low cost. As a recording medium appropriate for this ink jet recording method, there are a paper of which the surface is coated with a pigment such as silica or the like to form a porous layer, and a product obtained by applying a resin that absorbs ink through dissolution or swelling to a plastic substrate (for example, a molded article or a film of a polyester, polymethyl methacrylate or a polycarbonate) through coating or printing. Examples of such a recording medium include an ink jet OHP (overhead projector) film and an optical disk.
As an ink absorption layer, an ink absorption layer cured and coated with an ultraviolet-curing or heat-curing resin having a hydrophilic group is generally formed on a substrate surface in many cases. This layer tends to be soluble in water. When water is sprayed on the image, the image is easily destroyed. Even if the ink absorption layer is itself not dissolved in water, it is swollen when the substrate having the image is dipped in water. As a result, the dye forming the image is easily escaped in water, and the image is disarranged (lack of a water resistance).
As a dye of ink for ink jet, a direct dye or an acid dye is often used, and addition of a cationic dye binder to an ink receiving layer is proposed to solve the above-mentioned defect (Japanese Patent Laid-Open No. 261,089/1986). However, a dye binder which can be incorporated into a water-soluble resin is itself water-soluble in many cases. Although a portion bound to a dye is water-insoluble, the other portion is water-soluble, making it hard to obtain a satisfactory water resistance of a film in an ink receiving layer.
Japanese Patent Laid-Open No. 10,438/1986 proposes that cationic polyvinyl alcohol (hereinafter referred to as "cationic PVA") or its crosslinked product is incorporated into an ink receiving layer as a water-soluble polymeric substance. In this instance, mere incorporation of cationic PVA does not provide a satisfactory water resistance of the ink receiving layer itself as is the case with a cationic dye binder. Meanwhile, when using the crosslinked product of cationic PVA, water resistances of both the ink receiving layer and the image are obtained, but cationic PVA has to be used as a water-soluble resin. The selection range of the binder is narrow, and a ratio of a cationic group in the ink receiving layer is hardly increased. In a full color application in which a large amount of ink is used in the recording, a dryability and a water resistance of ink are not satisfactory. In addition, Japanese Patent Laid-Open No. 141,584/1986 proposes that an absorption of ink is improved by incorporating amorphous silica in a water-soluble resin. Further, the use of porous substances, for example, clay, talc, diatomaceous earth, calcium carbonate, calcium sulfate, barium sulfate, aluminum silicate, synthetic zeolite, alumina, zinc oxide, lithophone, and inorganic pigment particles such as titanium white is proposed (Japanese Patent Laid-Open No. 228,984/1986, and Japanese Patent Publication No. 1,706/1992). These methods improved the absorption of ink, but were still unsatisfactory in the full color application.
It is an object of the present invention to develop a photosensitive resin composition which exhibits a rapid ink absorption, which has an excellent water resistance, and which is appropriate for providing an ink receiving layer forming a sharp ink dot shape and having an excellent color formability of ink.